Transformers are common and necessary components in electric power distribution networks. Generally, electric power is distributed from electrical substations at high voltage typically in excess of 6,000 volts to minimize losses. Transformers are required to step the voltage down to lower levels, such as 120 volts, for local distribution to commercial and residential customers.
A transformer commonly used for this purpose is housed in a steel cabinet on a concrete platform or pad at ground level. The transformer itself includes primary and secondary coils housed in an oil-filled transformer well, the oil being provided to keep the coils cool. Studs, to which conductors carrying high voltage power to the primary coils, and to which conductors carrying stepped down voltage from the secondary coils, may be attached, protrude laterally outward from the transformer through the wall of the transformer well.
The studs are insulated from the wall of the transformer well by an insulating bushing or seal, which must be impermeable to the oil filling the transformer well. There are generally five studs, two for attaching incoming conductors to the primary side and three for attaching outgoing conductors to the secondary side. Three studs are required on the secondary side, one for each of two phases and one for a return or ground conductor.
Transformers of this type may be used to deliver electric power to a relatively small number of end consumers. To supply each such consumer, one conductor from each of the three studs on the secondary side of the transformer is required. Typically, then, a number of conductors is connected to each of the studs, one for each of the consumers being served.
Multi-tap stud connectors are used to attach the conductors individually to the studs. A common connector may be considered to be an extension of the stud itself, as it is attached to the stud and extends laterally outward from the wall of the transformer well. A plurality of conductor ports, arranged axially along this type of connector, are directed perpendicularly to the axis of the connector. Each conductor port has its own set screw for securing a conductor therein. These, too, are arranged axially along one side of the connector.
Perhaps the most serious shortcoming of this type of connector is the moment, or torque, it places on the stud when conductors are secured into the conductor ports. It is quite common for this moment to cause the bushing or seal separating and insulating the stud from the wall of the transformer well to fail. The most common result of such failure is oil leakage from the transformer well.
Another serious shortcoming is the relative inaccessibility of the conductor ports closest to the stud on the connector. To reach a set screw for a conductor port axially closest to the stud along the conductor, the electrician must reach in toward the stud over a number of conductors. Worse still, the inner set screws may not be readily visible, forcing the electrician to work blindly. And, as the three studs are often arranged one above the other on the wall of the transformer well, the electrician may often be required to reach between two layers of conductors to adjust the set screw of a conductor attached close to a stud.
Attempts have been made to address these problems. One such attempt is known as the Z-Bar connector because of its Z-shaped cross section. Such a connector is manufactured by Preformed Line Products under the name CONPACT Connector. Like the above-described connector, it may be considered to be an extension of the stud itself, because it is attached to the stud and extends laterally outward from the wall of the transformer well. In the Z-Bar connector, however, conductor ports are arranged axially therealong in two tiers, each conductor port again being directed perpendicularly to the axis of the connector, and each having a set screw on one side of the connector. The Z-bar connector permits the same number of conductors to be attached to the stud in one-half of the lateral distance, thereby reducing the moment applied to the stud by half, although the accessibility problems discussed above are somewhat reduced, but remain serious.
Commonly, multi-tap stud connectors have non-conductive covers to insulate the connectors from other connectors and the electrician. Prior art covers have generally been one-piece, rubber-like covers made from a plastisol, and fit over the connectors in a manner similar to that of a sock. However, these prior art covers are only appropriate for the prior art connectors. Since the prior art connectors are axial extensions of the transformer stud, they readily accept a sock-like cover that is applied axially. However, the sock-like prior art covers offer little versatility and are not useful for connectors having elements that are transverse to each other.
Although, a basic, rubber-like two-piece cover is known in the art for surrounding Z-Bar-type connectors, it does not overcome all of the limitations of the sock-like covers. Most importantly, the prior two-piece cover fails to provide a strong attachment between the two pieces.
An example of a prior art multi-tap stud connector and cover is disclosed in U.S. Pat. No. 4,214,806 to Kraft. Examples of prior art connectors for multiple connections are disclosed in U.S. Pat. No. 2,943,294 to Norden; and in foreign patent documents: DE 1116294 to Eigirt; and DE 1244906 to Hensel.
Thus, there is a continuing need to provide improved multi-tap stud connectors and non-conductive covers therefor. The present invention represents a novel approach toward a solution of the problems involved in connecting many conductors to the studs on a transformer and providing covers for such connectors. This invention addresses this need in the art along with other needs that will become apparent to those skilled in the art from this disclosure.